How to Balance Chemistry Equations — Free Online Tool (2026)

You can balance chemical equations instantly using the brevio Chemistry Equation Balancer — free, no signup, runs entirely in your browser. Enter an equation like H2 + O2 -> H2O and get the balanced result with coefficients in one click.

How to Use the Tool

1. Open the brevio Chemistry Equation Balancer. No account required.
2. Type your equation using the format: reactants on the left, products on the right, separated by ->. Separate multiple compounds with +. Example: CH4 + O2 -> CO2 + H2O.
3. Click Balance Equation. The tool finds the smallest integer coefficients that balance all atoms on both sides.
4. Or click any example in the list below the input to load a pre-set equation.

The Law of Conservation of Mass

A chemical equation is balanced when the number of atoms of each element is equal on both sides of the reaction arrow. This reflects the law of conservation of mass: matter is neither created nor destroyed in a chemical reaction, only rearranged. Coefficients (the numbers in front of each formula) indicate how many molecules of each substance participate in the reaction.

For example, the unbalanced equation H2 + O2 → H2O has 2 hydrogen atoms and 2 oxygen atoms on the left, but only 2 hydrogen and 1 oxygen on the right. The balanced form 2H2 + O2 → 2H2O gives 4 hydrogen and 2 oxygen on each side.

How the Balancing Algorithm Works

The tool uses a trial-and-error search over small integer coefficients (1–8) for each compound. For each candidate combination, it checks whether every element is conserved. While this brute-force approach would be slow for very large equations, it is fast and reliable for the common two- to four-compound equations encountered in secondary and undergraduate chemistry.

More rigorous balancing algorithms use linear algebra (Gaussian elimination) to solve a system of equations derived from the stoichiometric matrix. Each element provides one equation; coefficients are the unknowns. The solution space yields the minimum integer coefficients.

Frequently Asked Questions

What equation format does the tool accept?

Use uppercase letters for element symbols (e.g. H, O, Fe). Subscript numbers immediately follow the element (e.g. H2O, Fe2O3). Separate reactants and products with -> or →. Separate compounds with +.

Why can the tool not balance some equations?

The brute-force approach covers coefficients up to 8. Equations requiring larger coefficients (rare in introductory chemistry) may not balance. Also, verify that your formula is chemically correct — typos in element symbols will cause failures.

Does this handle parentheses like Ca(OH)2?

The current implementation uses a simplified parser that works for most common equations without parentheses. Equations with grouped formulas like Ca(OH)2 may require you to expand them first: Ca + 2OH.

Is this free to use?

Yes, completely free with no signup required. All computation runs in your browser.